EGR冷却温度对重型柴油机性能及排放的影响

以一台配有废气再循环(exhaust gas recirculation,EGR)冷却系统和可变几何截面涡轮增压器的高压共轨重型柴油机作为研究对象,进行了EGR冷却温度对柴油机性能及排放影响的台架试验研究。结果表明:随着EGR冷却温度降低,柴油机燃油消耗率、烟度和NOx排放均持续降低。而EGR冷却温度每降低1℃,柴油机燃油消耗率、烟度和NOx排放在不同转速、负荷下降幅差异明显。燃油消耗率在中等转速、低负荷工况降幅最大,NOx排放和烟度在高转速、低负荷工况下降幅最大;在考虑到EGR冷却系统消耗的能量后,可以通过计算得到理论燃油消耗率。在兼顾燃油消耗率和排放性的原则下得到了各工况下EGR相对最优冷却温度,而所得到的相对最优EGR冷却温度正是各个试验工况下理论燃油消耗率最低的温度。     

柴油机EGR电控冷却系统试验研究

研究了 CA498 柴油机在不同工况下EGR冷却温度对NOx等排放的影响规律,确定了各个工况下EGR的最佳冷却温度,据此设计出一套EGR冷却温度控制装置,可以通过单片机控制伺服电动水泵的转速来调节冷却水的循环量,确保不同工况下的最佳EGR冷却温度.将该电控冷却系统在CA498柴油机上进行了试验.结果表明,与未冷却的EGR系统相比,该EGR电控冷却系统在c0和Hc的排放略有增加的情况下,可以有效地降低NOx的排放、烟度和油耗率.     

可变二级增压柴油机变海拔工作特性数值模拟

以两级增压共轨重型柴油机为研究机型,采用GT-Power构建了其一维热力学仿真模型,对比可变二级增压(RTST)柴油机随高压级可变截面涡轮增压器(VGT)在不同叶片开度(20%~100%,)及不同海拔(0~4,km)下的工作特性.结果表明:不同转速工况下,空燃比和泵气损失随VGT叶片开度和海拔高度增加而降低.不同海拔下,随VGT叶片开度增大,低速时转矩与有效热效率先升高、后降低,高速时显著增大.随叶片开度和海拔增加,NO_x排放降低,soot排放大幅升高.海拔为4,km时,叶片开度从20%,增至100%,,低、高速工况的转矩和有效热效率均分别增加7.5%,和39.2%,,NO_x排放分别降低38%,和24%,;海拔为2,km时,不同转速工况下柴油机匹配RTST均能实现较高的EGR率(超过60%,).VGT叶片开度减小,EGR率快速增大,转矩及有效热效率降低,有效燃油消耗率(BSFC)逐渐增加,NO_x排放快速降低,soot排放先升高后降低.在EGR率约为35%,时,RTST柴油机综合性能达到最佳.     

采用防爆EGR+DOC实现防爆柴油机低排放的研究

防爆柴油机以动力性强、经济性好的特点已得到广泛应用,但排放污染严重。煤矿行业日益严格的排放法规对防爆柴油机技术不断提出新的挑战,如何在保持不降低防爆柴油机动力性的同时有效处理有害废气排放产物是当前煤矿井下所遇到的难题。针对防爆柴油机尾气中NO_x和CO两种有害产物,采用了在电控防爆柴油机的进气和排气系统上布置防爆EGR+DOC的技术方案,并根据GB 20891—2014的要求对加装防爆EGR+DOC前后进行了八工况排放试验研究,试验结果表明：采用防爆柴油机在各个工况条件下NO_x和CO的排放量均有所下降,NO_x排放最高降低了36.6%,CO排放最高降低了36.3%。采用防爆EGR+DOC技术具有改造简单、成本低、效果明显、可靠性高的优点,防爆EGR+DOC技术的应用对煤矿井下环境的治理和保护有着非常重要的意义。     

满足车用国Ⅳ排放标准的EGR与DOC技术的应用研究

为实现车用柴油机大流量废气再循环,研制了氧化催化转化器(DOC)后处理器与大流量冷却式废气再循环(L-CEGR)系统组成的排放控制新技术配置,并在11L车用发动机上进行了试验。试验结果表明:采用电控可变几何涡轮增压器(VGT)为主件的L-CEGR系统使NOx排放下降28.6%;采用160MPa高压喷射和进气优化后,PM排放降低74.4%,铂含量为0.55g/unit的DOC能使PM排放降低20%;柴油机各项排放指标均达到国Ⅳ标准,也符合NO2排放限值要求;L-CEGR与160MPa高压喷射等技术相结合,使发动机加权平均燃油消耗率降低3.5%。     

EGR率对船用柴油机中低负荷燃烧排放性能影响的仿真及试验研究

在船用高压共轨柴油机TBD234V6上进行了中低负荷工况下EGR率对柴油机燃烧排放性能影响的试验研究。应用AVL-FIRE软件建模,对柴油机缸内燃烧过程进行CFD仿真分析。仿真和试验研究结果表明:中低负荷工况下采用EGR能够有效降低NO_x的排放。EGR率较小时,对柴油机的性能影响较小;当EGR率较大时,柴油机的工作性能恶化,soot排放迅速增多。特定工况下的CFD模拟结果显示:随着EGR率的增加,燃烧过程的最高压力和最高温度降低,放热速率减小,燃烧过程变得平缓。     

进气涡流对车用直喷式柴油机微粒排放的影响

用自行设计的喷气式可变涡流进气系统（ＡＩＶＳＩＳ）调节气缸内的涡流水平,试验研究了进气涡流对连用直喷式柴油机微粒排放的影响。结果表明,中速工况为较低的微粒比排放工况,螺旋进气道形成的涡流水平基本可以满足燃料燃烧的要求,改变涡流水平对改善柴油机微粒排放贡献不大。而低速高负荷工况是柴油机较高的微粒比排放区,适度提高气缸内的涡流水平,可以有效降低柴油机微粒的排放量,使微粒降低的主要因素是不可溶组分排放的降低。高速工况螺旋进气道形成的涡流水平较高。降低气缸内的涡流水平可以降低柴油机微粒的排放量,使微粒排放降低的主要因素是可溶性有机组分排放的降低。     

利用EGR降低柴油机排放的研究

介绍了废气再循环（ＥＧＲ）降低柴油机ＮＯｘ排放的原理和控制方法,考察了不同工况下柴油机废气污染物的排放分布情况,并进行了柴油机废气再循环的试验。试验结果表明,在柴油机稍作更改,成本增加不多的基础上,采用ＥＧＲ能够较有效地降低ＮＯｘ排放。     

基于VGT的EGR对电控柴油机影响的试验研究

在一台电控共轨柴油机上,进行了基于可变涡轮截面增压器(VGT)控制的废气再循环(EGR)对柴油机燃烧、性能和排放影响的试验研究.系统研究了VGT开度、EGR率和喷油参数对柴油机性能和排放的影响.研究表明,采用基于VGT控制的EGR系统,调整VGT叶片位置,可以改变EGR率,实现最高43.2%的EGR率,从而有效地降低NOx;在调整优化喷油参数后,柴油机的排放有了很大的改善,烟度有较大幅度的降低,经过优化,气体排放可满足国Ⅳ排放法规的要求,十三工况加权当量比油耗比原国Ⅲ柴油机降低了4.2%,但是,采用EGR方案缸内最大爆发压力明显增大.     

燃料挥发性对柴油机性能及排放的影响

针对不同的发动机热状态及压缩比，试验研究了燃料物化特性对柴油机稳态及过渡工况下性能、排放的影响规律。应用自行开发的柴油机过渡工况控制系统及排气采集装置，模拟车用柴油机实际工作时的加速状态，对具有相同十六烷值但有不同挥发性能燃料的HC排放特性进行了研究，利用气相色谱仪对HC排放成分进行了分析。研究结果表明，采用挥发性好的燃料，可有效降低排气烟度，提高有效热效率，在发动机热状态不好及压缩比较低等燃烧条件恶劣、HC排放高的情况下，可有效地降低HC排放。     

内燃机车柴油机停缸节油技术设计研究

停缸节油技术能够解决内燃机车柴油机长时间空载状态下功率需求、燃油消耗、有害气体排放之间的矛盾。详细介绍了柴油机在0.33,0.5,0.66三种功率比率下的停缸技术下点火控制,给出了工作状态机逻辑图和转换约束条件。研究表明,与柴油机正常模式工作相比,使用停缸节油技术可节约空载燃油20%以上,具有非常好的经济价值。     

Experimental investigations of performance and emissions of Karanja oil and its blends in a single cylinder agricultural diesel engine

An experimental investigation has been carried out to analyze the performance and emission characteristics of a compression ignition engine fuelled with Karanja oil and its blends (10%, 20%, 50% and 75%) vis-a-vis mineral diesel. The effect of temperature on the viscosity of Karanja oil has also been investigated. Fuel preheating in the experiments – for reducing viscosity of Karanja oil and blends has been done by a specially designed heat exchanger, which utilizes waste heat from exhaust gases. A series of engine tests, with and without preheating/pre-conditioning have been conducted using each of the above fuel blends for comparative performance evaluation. The performance parameters evaluated include thermal efficiency, brake specific fuel consumption (BSFC), brake specific energy consumption (BSEC), and exhaust gas temperature whereas exhaust emissions include mass emissions of CO, HC, NO and smoke opacity. These parameters were evaluated in a single cylinder compression ignition engine typically used in agriculture sector of developing countries. The results of the experiment in each case were compared with baseline data of mineral diesel. Significant improvements have been observed in the performance parameters of the engine as well as exhaust emissions, when lower blends of Karanja oil were used with preheating and also without preheating. The gaseous emission of oxide of nitrogen from all blends with and with out preheating are lower than mineral diesel at all engine loads. Karanja oil blends with diesel (up to 50% v/v) without preheating as well as with preheating can replace diesel for operating the CI engines giving lower emissions and improved engine performance.     

生物柴油的排放试验研究

通过对燃烧生物柴油发动机排放污染物的测量和分析,探讨了生物柴油降低柴油机排气污染物的机理。分析了不同配比的生物柴油燃烧污染物随发动机转速、负荷的变化规律,得到了生物柴油的最佳配比方案。研究结果表明:生物柴油可以有效地降低柴油机的排气污染物,尤其是颗粒污染物;随着生物燃料中油酸甲脂含量的增加,柴油机的各种排气污染物均有不同幅度的降低。     

Performance and emission evaluation of a CI engine fueled with preheated raw rapeseed oil (RRO)–diesel blends

Many studies are still being carried out to find out surplus information about how vegetable based oils can efficiently be used in compression ignition engines. Raw rapeseed oil (RRO) was used as blended with diesel fuel (DF) by 50% oil–50% diesel fuel in volume (O50) also as blended with diesel fuel by 20% oil–80% diesel fuel in volume (O20). The test fuels were used in a single cylinder, four stroke, naturally aspirated, direct injection compression ignition engine. The effects of fuel preheating to 100 °C on the engine performance and emission characteristics of a CI engine fueled with rapeseed oil diesel blends were clarified. Results showed that preheating of RRO was lowered RRO’s viscosity and provided smooth fuel flow Heating is necessary for smooth flow and to avoid fuel filter clogging. It can be achieved by heating RRO to 100 °C. It can also be concluded that preheating of the fuel have some positive effects on engine performance and emissions when operating with vegetable oil.     

现代发动机冷却系统的发展趋势

传统发动机冷却系统由于自身的被动性影响，其工作性能受到限制。在部分负荷时会造成功率损失，而汽车在此工况下行驶的时间最长。介绍一些先进冷却系统的设计和工作特点，这些系统既能起到保护发动机的作用，又能改善燃油效率和降低排放污染物。     

Effects of intake air temperature on SI engine emissions during a cold start

This paper presents the concept of preheating the intake air to reduce cold-start emissions from gasoline engines. The effects of intake air temperature on emissions from a gasoline engine were studied by using an air heater based on spark ignition. A light-duty vehicle test of cold-start emissions was carried out at an ambient temperature of?7°C according to New European Driving Cycle for Euro 3 and Euro 4 exhaust emission legislations. The results showed that preheating the intake air could effectively reduce both hydrocarbon (HC) and carbon monoxide (CO) emissions and improve fuel economy during a cold start. During idling conditions, the key phase of the HC and CO emissions was the first 40 s. With the aid of the air heater, cold-start HC and CO emissions from the vehicle were lower than the limit values in the Euro 3 and Euro 4 regulations.     

采用VNT/EGR和DOC降低柴油机排放的试验

在一台高压共轨柴油机上进行了采用基于可变喷嘴环涡轮增压器(VNT)的废气再循环(EGR)系统(VNT/EGR)和柴油机氧化催化器(DOC)降低排放的试验研究。结果表明,通过调节VNT开度可以有效实现EGR循环和控制EGR率,显著降低NOx排放,并且在一定EGR率范围内对烟度影响较小。提高喷射压力可以较明显改善NOx和烟度的折衷关系,采用合理的后喷参数能够在不明显影响经济性和NOx排放的前提下显著降低烟度。对燃烧室进行降低压缩比的合理设计也可以明显改善NOx和烟度的折衷关系。在燃烧系统优化的基础上,最终加装DOC的ESC循环排放测试结果满足了国Ⅳ要求,其中PM为0.0191g/(kW·h),NOx为2.88g/(kW·h),HC和CO排放远低于国Ⅳ限值。     

喷射参数对二甲醚发动机NO_x排放的影响

以6105型压燃式二甲醚发动机为对象,研究了喷射系统的喷射压力、喷孔直径和供油提前角对二甲醚发动机外特性NOx排放的影响。试验结果表明:在外特性的整个转速范围内,NOx排放随发动机转速的升高而降低;在发动机转速较低时,NOx排放随喷射压力的升高而降低,高速时则反之;在发动机低速工况下,喷孔直径较小的喷油器NOx排放低,高速时大孔径的喷油器NOx排放低;喷油器针阀开启压力较高时,通过推迟供油提前角来控制NOx排放的效果较好,喷油器针阀开启压力较低时该效果不明显。     

Investigations on the performance and exhaust emissions of a diesel engine using preheated waste frying oil as fuel

In the present experimental investigation, waste frying oil a non-edible vegetable oil was used as an alternative fuel for diesel engine. The high viscosity of the waste frying oil was reduced by preheating. The properties of waste frying oil such as viscosity, density, calorific value and flash point were determined. The effect of temperature on the viscosity of waste frying oil was evaluated. It was determined that the waste frying oil requires a heating temperature of 135 °C to bring down its viscosity to that of diesel at 30 °C. The performance and exhaust emissions of a single cylinder diesel engine was evaluated using diesel, waste frying oil (without preheating) and waste frying oil preheated to two different inlet temperatures (75 and 135 °C). The engine performance was improved and the CO and smoke emissions were reduced using preheated waste frying oil. It was concluded from the results of the experimental investigation that the waste frying oil preheated to 135 °C could be used as a diesel fuel substitute for short-term engine operation.